1. Technical Field
The exemplary embodiments relate to semiconductor technology, and more particularly, to a variable resistor, a non-volatile memory device using the same, and methods of fabricating the same.
2. Related Art
In recent years, with increase in demand for portable digital application devices such as digital cameras, MP3 players, personal digital assistants (PDAs), and portable phones, the nonvolatile memory market is rapidly expanding. As flash memory devices which are programmable nonvolatile memory devices reach the limit of scaling, nonvolatile memory devices such as phase-change random access memory (PcRAM) devices or resistive random access memory (ReRAM) devices using a variable resistor of which a resistance value is reversibly changed, have received attention as nonvolatile memory devices which are an alternative to the flash memory devices. Since the nonvolatile memory devices utilize their intrinsic physical properties as data digits, a memory cell configuration is simple and thus high densification of the memory device is realized.
Compared with the PcRAM devices, ReRAM devices are advantageous in that pulse control over the device is easy and driving current is low. Thus, it is advantageous in terms of scalability and power consumption. The ReRAM devices include (i) a unipolar switching type in which a set voltage and a reset voltage are exhibited at the same polarity state, and (ii) a bipolar switching type in which the set voltage and the reset voltage are exhibited at different polarity states. In general, the ReRAM device of a bipolar switching type has a stable resistive switching characteristic as compared with the ReRAM device of a unipolar switching type, because the bipolar switching type has a stable resistive switching characteristic and is capable of being driven with relatively low current.